In piping systems, elbows are fittings used to change the direction of the pipeline. By angle, there are three commonly used types: 45°, 90°, and 180°, as well as other non-standard angles like 60° according to engineering requirements. Elbow materials include cast iron, stainless steel, alloy steel, malleable cast iron, carbon steel, non-ferrous metals, and plastics.

Ways to connect pipes include direct welding (the most common method), flange connection, hot melt connection, electric fusion connection, threaded connection, and socket connection, etc. According to the production process, they can be classified into: welded elbows, stamped elbows, extruded elbows, cast elbows, and socket-welded elbows, etc. Other names: 90-degree elbows, right-angle elbows, etc.